Interaction of calmodulin with troponin I and the troponin-tropomyosin-actin complex. Effect of Ca2+ or Sr2+ ions

K. Yamamoto, H. Nakayama, K. Nunoi, M. Fujishima

    Research output: Contribution to journalArticlepeer-review

    5 Citations (Scopus)

    Abstract

    In an effort to elucidate the mechanism of calmodulin regulation of muscle contraction, we investigated the interaction between calmodulin and troponin components in the presence of Ca2+ or Sr2+ by the use of ultracentrifugation methods and polyacrylamide-gel electrophoresis. Skeletal-muscle troponin C bound to troponin I and dissociated it from the tropomyosin-actin complex in the presence of Ca2+ or Sr2+. When troponin T was absent, calmodulin bound to troponin I and dissociated it from the tropomyosin-actin complex in the presence of Ca2+ or Sr2+. When troponin T was present, calmodulin hardly bound to troponin I even in the presence of bivalent cations. Trifluoperazine, a calmodulin antagonist, inhibited the bivalent-cation-dependent interaction between calmodulin and troponin I. Calmodulin migrated more slowly in the presence of Sr2+ than it did in the presence of EGTA but faster than it did in the presence of Ca2+ on polyacrylamide-gel electrophoresis under non-denaturing conditions. It is concluded that troponin T is not required in the calmodulin regulation of muscle contraction because troponin T inhibits the bivalent-cation-dependent interaction between calmodulin and troponin I and because calmodulin binds to troponin I and dissociates it from the tropomyosin-actin complex in a bivalent-cation-dependent manner. Sr2+-induced exposure of the hydrophobic region enables calmodulin to bind to troponin I, as is the case with Ca2+.

    Original languageEnglish
    Pages (from-to)905-909
    Number of pages5
    JournalBiochemical Journal
    Volume241
    Issue number3
    DOIs
    Publication statusPublished - 1987

    All Science Journal Classification (ASJC) codes

    • Biochemistry
    • Molecular Biology
    • Cell Biology

    Fingerprint Dive into the research topics of 'Interaction of calmodulin with troponin I and the troponin-tropomyosin-actin complex. Effect of Ca<sup>2+</sup> or Sr<sup>2+</sup> ions'. Together they form a unique fingerprint.

    Cite this